Chicago Transit Authority spokeswoman Lambrini Lukidis said video from the scene shows no driver at the controls of an empty train that crashed into another train carrying passengers Monday morning.

As many as four dozen people were hurt, though officials say none of the injures was life threatening.

Lukidis says the video has been turned over to the National Transportation Safety Board, which is investigating.

The empty train was eastbound when it hit a westbound train that was stopped at the Blue Line's Harlem station in Forest Park. The CTA says the station has about 4,000 boards each weekday. Forest Park is about 10 miles west of downtown Chicago.